Do people care about religion?

It looks like this week is going to be a heavy religious themed week.  In particular I wanted to talk a little more about a comment that Sthenno made on my post yesterday, specifically

Most people tend to believe the same things their families do on most issues - particularly those issues that they never have cause to put a lot of thought into. We could regard the trend of sharing your parents' religion as evidence that most people just don't actually care that much about religion, so it's never worth their time thinking about it.

I think this is a very telling observation.  Many people obviously care a great deal about religion in that they have strong feelings about other people based on whether or not their religions are the same.  However, just because someone cares very much whether or not someone else is part of their religion has basically nothing to do with the details of the religion.  If you consider the incredible violence that has taken place in the world between religions with only very slightly different ideas it becomes clear that religious disagreements are clearly about the us vs. them mentality and not at all about the difference in details.  If the details were really the issue then one would assume that everyone within a religion must have a tremendous grasp of the ins and outs of their beliefs and the exact differences with other groups but surely this is not the case - most people involved in religious conflict just know that they other side is wrong and they are right.  You might also expect that if conflict were in some way due to the differences in beliefs that the conflict would be greater with greater differences in belief but that is not at all the case - Buddhists have a much greater difference of belief with Christians than the various Christian sects do with one another but yet the Buddhist/Christian violence isn't greater than the violence between various Christian sects.

Another powerful note is that religious people very often pay absolutely no attention to the supposedly infallible and divinely inspired holy documents their religion reveres.  Reading the whole Bible isn't something rare just amongst atheists, it is rare amongst everyone, including those who theoretically think it is the source of all morality and a direct translation of God's will.  I know that if I really thought that a book contained the literal word of the creator of the universe and contained within it the instructions for living according to that creator I would have the entire thing memorized and yet many/most religious people who claim to believe that exact thing have skimmed a few pages here and there.

Clearly people feel very strongly about religion but only in the sense that it defines 'us vs. them.'  Certainly if people were really interested in the details they would learn about them (they don't, by and large) and if the details were important to their acceptance of a religion there would be a smaller percentage of people who take up the religion of their parents/region/culture.  So most people just take up a religion because it is what surrounds them, ignore the details and use it as a definition of tribal allegiance.  There are people out there who choose a religion based on the specifics of the religion instead of simple proximity but those are very much in the minority.